6xxx-series aluminum alloy sheet for inner panel of hood, and preparation method and use thereof

Abstract

The present disclosure provides a 6xxx-series aluminum alloy sheet for an inner panel of a hood, and a preparation method and use thereof. The aluminum alloy sheet includes the following compositions in percentage by weight: 0.75%-0.95% of Si, 0.15%-0.35% of Mg, 0.2%-0.4% of Fe, 0.05%-0.2% of Mn, 0.06%-0.2% of Cr, less than or equal to 0.15% of Cu, and less than or equal to 0.15% of inevitable impurities in total amount, where each inevitable impurity is less than or equal to 0.05%, the balance is Al, and an atomic ratio of Mg to Si is (0.18-0.54):1. The sheet has high formability hood. After baking, the sheet has low yield strength on the premise of maintaining strength slightly exceeding strength requirement of a support structure, and further has a low strain rate sensitivity coefficient, satisfying the pedestrian protection requirement. The aluminum alloy sheet is conducive to recycle and remanufacture.

What is claimed is: 
     
         1 . A 6xxx-series aluminum alloy sheet for an inner panel of a hood, wherein comprises the following compositions in percentage by weight: 0.75%-0.95% of Si, 0.15%-0.35% of Mg, 0.2%-0.4% of Fe, 0.05%-0.2% of Mn, 0.06%-0.2% of Cr, less than or equal to 0.15% of Cu, and less than or equal to 0.15% of inevitable impurities in total amount, wherein each inevitable impurity is less than or equal to 0.05%, the balance is Al, and an atomic ratio of Mg to Si is (0.18-0.54):1; and
 a yield strength of the aluminum alloy sheet is less than or equal to 80 MPa, a elongation is greater than or equal to 25%; and after baking, the yield strength of the aluminum alloy sheet is 110-145 MPa, a 0.2% strain rate sensitivity coefficient is less than or equal to 0.005, and a 10% strain rate sensitivity coefficient is less than or equal to 0.003.   
     
     
         2 . The aluminum alloy sheet according to  claim 1 , wherein comprises the following compositions in percentage by weight: 0.8%-0.85% of Si, 0.22%-0.32% of Mg, 0.25%-0.35% of Fe, 0.05%-0.1% of Mn, 0.06%-0.1% of Cr, less than or equal to 0.06% of Cu, and less than or equal to 0.15% of the inevitable impurities in total amount, wherein each inevitable impurity is less than or equal to 0.05%, the balance is Al, and the atomic ratio of Mg to Si is (0.30-0.47):1. 
     
     
         3 . A preparation method of the 6xxx-series aluminum alloy sheet for an inner panel of a hood according to  claim 1 , wherein comprises the following steps:
 step S1, subjecting raw materials of the 6xxx-series aluminum alloy to mixing and casting in a composition ratio to obtain an aluminum alloy ingot;   step S2, subjecting the aluminum alloy ingot to homogenization treatment to obtain a homogenized ingot;   step S3, directly discharging the homogenized ingot out of a furnace for hot rolling to obtain a hot-rolled coil, and then subjecting the hot-rolled coil to carry out cold rolling on the hot-rolled coil to obtain a cold-rolled coil; and   step S4, subjecting the cold-rolled coil to solute solution treatment to obtain a solute solution coil, then subjecting the solute solution coil to pre-aging treatment to obtain a finished temper coil, and finally slicing the finished temper coil to obtain the 6xxx-series aluminum alloy sheet.   
     
     
         4 . The preparation method according to  claim 3 , wherein in the step S2, the homogenization treatment is conducted at a temperature of 470-540° C. for 4-20 h. 
     
     
         5 . The preparation method according to  claim 4 , wherein in the step S2, the homogenization treatment is conducted at the temperature of 500-520° C. for 8-14 h. 
     
     
         6 . The preparation method according to  claim 3 , wherein in the step S3, the hot rolling is conducted at an initial rolling temperature of 470-540° C., and a finish rolling temperature of 250-300° C., and the thickness of hot-rolled coil is 3-8 mm. 
     
     
         7 . The preparation method according to  claim 3 , wherein in the step S3, the thickness of cold-rolled coil is 0.8-1.5 mm. 
     
     
         8 . The preparation method according to  claim 3 , wherein in the step S4, the solute solution treatment comprises: heating the cold-rolled coil to 460-530° C. at a speed greater than 200° C./min, carrying out heat retention for 5 s-1 min, and then cooling to room temperature at a speed greater than 10° C./s. 
     
     
         9 . The preparation method according to  claim 3 , wherein in the step S4, the pre-aging treatment comprises: heating the solute solution coil to 70-100° C. in a pre-aging furnace at a speed greater than 80° C./min, then discharging a heated coil out of the pre-aging furnace for coiling, wherein a temperature drop is less than 10° C. during a period from discharging to coiling, then transferring a coiled coil to a heat retention furnace, carrying out heat retention at 60-90° C. for 2-10 h, and then cooling to room temperature. 
     
     
         10 . A use of the 6xxx-series aluminum alloy sheet for an inner panel of a hood according to  claim 1  in an inner panel of a hood of an automobile.